198305_voc_epa450_3-83-012_plywood_dryers

7/30/2019 198305_voc_epa450_3-83-012_plywood_dryers

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United States Office of Air Quality EPA-450/3-83-012Environmental Protection Planning and Standards May 19 8 3&enW Research Triangle Park NC 2 7 7 1 1Air

ControlTechniquesfor OrganicEmissions fromPlywoodVeneer Dryers


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w,. fi '";3$=!N I TED STA TES EN VI R ON M EN TA L PR OTEC TI ON A GEN CYResearch Triangle Park, N orth Carolina 27 71 1f .4~

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--UG 2 2 f983 - R - - - - - - ~Dear S i r o r Madam:

Enclosed f o r your information i s a document en t i t l ed "Control Techniquesfor Organic Emissions from Plywood Veneer Dryers." T h i s r e p o r t s u m a r i z e sinformation gathered by the U. S. Environmental Protection Agency on thecon tro l of m i ss io ns from softwood plywood manufacturing.Thi s c on tro l techn ique document (CTD) , unl ike a co ntr ol techniquesguide1 in e ( C T G ) , does not de fin e reasonable ava i l ab le c ontro l techno1 ogy( R A C T ) . I t s di sc us sio n of con tro l technology, however, may be used by aSt a t e as background mate r ia l fo r deve loping i t s own emission reg ula t i on s .Encl osed , a1 so , i s a 1 i s t of persons who have been se nt the re po rta t t h i s tim e.

S i n c e r e l y ya& Jack R . Farmer .D i r e c t o rEmission Standards andEngineering Division2 Enclosures


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Control Techniques for Organic Emissionsfrom Plywood Veneer Dryers

Emission Standard s and Engineering Division

U.S. ENVIRONMEN TAL PROTECTION AGENCYOffice of Air, No ise, and R adiationOffice of Air Q uality Planning and Standa rdsResea rch Triangle P ark, North CarolinaOctober 1982


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Th is repor t has been rev ie wed by the Em iss ion S tandards and Eng ineer ing D iv i s ion o f the O f f i ce o f A i r Q ua lP l a n n i n g a n d S ta n da r d s, E P A, a n d a p p r ove d f o r p u b l i ca t io n , Me n t i o n of t r a d e n a m e s o r c o mm e r c i a l p ro d u c t s i s nin tend ed o cons t i tu te endorsem ent o r recom mend a t ion fo r use . Cop ies of th i s repor t a re ava i lab le th rough th e L ib raServ i ces O f f i ce (MD -35 ) . U .S . Env i ron me nta l P ro tec t i on Agency , Research Tr iang le Park , N .C. 277 1 1 , o r f roNa t iona l Techn ica l In fo rm at ion Serv i ces , 528 5 Por t Roya l Road , Spr ing fi e ld , V i rg in ia 22161 .


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TABLE OF CONTENTS

C h a p t e r1 I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . 2 S o u r c e s an d T yp es o f E m i s s i o n s . . . . . . . . . . . . .

2 .1 P r o d u c t C h a r a c t e r i z a t i o n . . . . . . . . . . . . . 2 .2 I n d u s t r y P r o f i l e . . . . . . . . . . . . . . . . .

2 . 2 . 1 M a r k e t s . . . . . . . . . . . . . . . . . . 2 . 3 Trends . . . . . . . . . . . . . . . . . . . . . . 2 .4 P r o c e s s e s a n d T h e i r E m i s s i o n s . . . . . . . . . . .

2 . 4 . 1 Green Processes . . . . . . . . . . . . . . 2 . 4 . 2 V e n e e r D r y i n g . . . . . . . . . . . . . . . 2 .4 .3 V e ne e r P r e p a r a t i o n . L a ya p . a nd G l d i n g . . .2.4 .4 P ly w oo d F i n i s h i n g . . . . . . . . . . . . . 2 .4 .5 Techno1 o g i c a l Changes . . . . . . . . . . .

2 .5 R e f e r e n c e s . . . . . . . . . . . . . . . . . . . . E m i s s i o n C o n t r o l T e ch n iq u es . . . . . . . . . . . . . . 3 . 1 I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . 3 .2 V e n e e r O r y e r E m i s s i o n C o n t r o l . . . . . . . . . . .

3 .2 . i Wet Sc rubb ing . . . . . . . . . . . . . . . 3 .2 .1 .1 Mu1t i p l e Spray Chambers . . . . . .3 .2 .1 .2 Cornbi n a t i o n Packed Tower andC y c l o n i c C o l l e c t o r s . . . . . . . . 3 . 2 . 1 . 3 Sand F i 1 e r S c ru bb er s . . . . . . . 3 .2 .1 .4 I o n i z i n g ;Je t S c ru b b e rs . . . . . .

3 . 2 . 2 i n c i n e r a t i o n . . . . . . . . . . . . . . . . 3 .2 .2 .1 3 o i l e r I n c i n e r a t i o n . . . . . . . . 3 .2 .2 .2 I n c i n e r a t i o n i n a F ue l C e l l . . . .3 .2 .2 .3 C a t a l y t i c I n c i n e r a t i o n . . . . . .

3 . 2 . 3 Low-Tenpera tu re Dryi ng . . . . . . . . . . . 3.2 .4 C o n t ro l o f F u g i t i v e D r y e r Em is s i on s . . . .

3 . 3 P a n e l S a nd e r E m i s s i o n C o n t r o l T e c h n i q u e s . . . . .3 . 3 . 1 H i g h - E ff i c i ency Cyc lones . . . . . . . . . . 3 .3 .2 F a b r i c F i l t e r s . . . . . . . . . . . . . . . 3.4 C c n c l u s i c n s . . . . . . . . . . . . . . . . . . . .

3 .5 R e f e r e n c e s . . . . . . . . . . . . . . . . . . . .

PaseI -1 2 - 1 2-1 2-1 2-4 2-6 2-9 2-10 2-12 2- 2 0 2-20 2-21 2 - 21 3-!3-1 3-1 3-1 3-2 3-2 3-4 3-4 3-6 3-5 3 - 3 3-12 3-!23-12 3-13 3-14 3-14 3-15 3-15


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TABLE OF CONTENTS (continued)C hap t e r Page

C o s t o f E m i s si o n s C o n t r o l . . . . . . . . . . . . . . . . 4 . 1 I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . 4.2 Model P la n ts . . . . . . . . . . . . . . . . . . . 4.3 Costs . . . . . . . . . . . . . . . . . . . . . . . 4.4 Refe rences . . . . . . . . . . . . . . . . . . . . E n v i r o r m e n t a l I m p ac t . . . . . . . . . . . . . . . . . . 5.1 A i r Pol 1u t o n I np a ct . . . . . . . . . . . . . . . 5 .2 W at er P o l l u t i o n I m pa c t . . . . . . . . . . . . . . 5.3 S o l i d W as te . . . . . . . . . . . . . . . . . . . . 5.4 Energy Imp ac t . . . . . . . . . . . . . . . . . . . 5.5 References . . . . . . . . . . . . . . . . . . . . Te s t :4ethods and Tes t Re su l t s . . . . . . . . . . . . . . 6.1 Veneer D r ye r Tes t Methods . . . . . . . . . . . . . 6.1.1 Oregon Department o f E n v i r o n m e n t al Q ua1it y (ODEQ) Method 7 . . . . . . . . . . . . . . 6 .1 .2 W a s h in g t on S t a t e U n i v e r s i t y ( 'ASU) P k t h o d . . 6.1.3 EPA Me thod 25 . . . . . . . . . . . . . . . 6.1.4 Co m bi n a ti o n EPA Me tho d 5X and EPA Method 25 . . . . . . . . . . . . . . . . . 6.2 P lywood Sander Te s t Wethod . . . . . . . . . . . . 5.3 R e s u l t s o f E m i s si o n T e s t i n g . . . . . . . . . . . . 6.3.1 V e n w r D r y e r s . . . . . . . . . . . . . . . 6.3.1 .1 i l n c on t r o l l ed E r n i ss ions . . . . . . 6.3.1 .2 E m i s s i o n T e s t s o f C o n t r o l 3 e v i c e s . 6.3.2 S t a t e R e g u l a t i o n s A pp l i c a b l e t o P ly wo od

P l a n t s . . . . . . . . . . . . . . . . . . . 6.3 .2 .1 Veneer C r ye r Co nt r o l evaluation . . 11.3.3 Plywood S a b de r s . . . . . . . . . . . . . . 6.4 Refe rences . . . . . . . . . . . . . . . . . . . .


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L IS T OF TABLES Nunber Page

P l y w o o d P r o d u c t i o n b y S t a- Le a n d R eg i o n . 1 38 0 . . . . . . 2 -22 - 2 Emp loymen t S ta t i s t i cs . . So f tn ood Veneer and P lywood . . . 2-5

P a r a m e te r s f o r ;4odel P l a n t 1 . . . . . . . . . . . . . . P a r a m e te r s f o r :lod e1 P l a n t 2 . . . . . . . . . . . . . . P a r a m e te r s f o r ;lo de 1 P l a n t 3 . . . . . . . . . . . . . . P a r a m e te r s f o r Plodel P l a n t 4 . . . . . . . . . . . . . . P a r a m e te r s f o r ?lod e1 P l a n t 5 . . . . . . . . . . . . . . P a r a rn e t e rs f o r :4odel P l a n t 6 . . . . . . . . . . . . . . Summary o f Y o d e l P l a n t P a r a m e t e r s . . . . . . . . . . . . C a p i t a l C o s t s o f C o n t r o l O p t i o n s f o r r4odel P l a n t sW i t h S t 2a m - He a te d D r y e r s . . . . . . . . . . . . . . . . C a p i t a l C o s ts o f C o n t r o l O p t i o n s f o r ;-lode1 P l a n t sLd i th D i r x t - F i r e d 3 r y e r s . . . . . . . . . . . . . . . . A nn ua l O p e r a t i n g C o s t s o f C o n t r o l O p t i o n s f o r ;lode1P l a n t s W i t h S t ea n -H e at 2d D r y e r s . . . . . . . . . . . . . A nn ua l O p e r a t i n g C o s ts o f C o n t r o l O p t i o n s f o r Yo de lP l a n t s w i t h D i r e c t - F i r 2 d D r ye r s . . . . . . . . . . . . . A n n ua l iz e d C o st s o f C o n t r o l O p t i on s f o r P l a n t s W i t hSt2am-!-kat2d Dryers . . . . . . . . . . . . . . . . . . . A n n u a l i z e d C o st s o f C o n t r o l O p t i on s f o r P l a n t sY i t h D i r e c t - F i r e d D r y e r s . . . . . . . . . . . . . . . . C a p i t a l C o s t s o f C o mp le te P ly wo od P l a n t s . . . . . . . . A nn ua l i z e d D i r 2 c t C o s t s o f C o mp le te P l y wo od P l a n t s . . .E s t i r n a t 2 d A i r P o l 1u t i o n I mp ac ts o f C o n t r o l C @ ti on sf o r +ode1 P l a n t s . . . . . . . . . . . . . . . . . . . . E s t i m at e s o f E l e c t r i c a l E ne rg y C o n su n 2t io n o f Y o de lP l a n t s . . . . . . . . . . . . . . . . . . . . . . . . .


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6- 1 E m i s si o n T e s t s o f U n c o n t r o l 1e d V en ee r 3 r y o r s D r y i n gD o u g l a s F i r s . . . . . . . . . . . . . . . . . . . . . . . 6-12 D i s t r i b u t ion Be tween Te rpene En i s s i ons and O th e rE m i s s i o n s . . . . . . . . . . . . . . . . . . . . . . . . 5 -14 T o t a l O r g a n i c E m i ss i o ns T e s t s o f U n c o n t r o l 1edV e n e e r D r y e r s . . . . . . . . . . . . . . . . . . . . . . 6-15 E m i s s i o n D a t a f o r W et S c r u b b e r s o n Ve ne er D r y e r s . . . . 6-17 E m i s si o n D a ta f o r S a n d a i r F i l t e r S ys te ms o n Ve ne erD r y e r s . . . . . . . . . . . . . . . . . . . . . . . . . 6-13 R e s u l t s o f EPA T e s t s o f a B o i l e r I n c i n e r a t i o n S ys te m--P a r t i c u l a t e an d C o n d e ns i b le O rg a n ic E m i s s io n s . . . . . . 6-19 R e s u l t s of EPA T e s t s o f a B o i l ? r I n c i n e r a t i o n S ys te m--P a r t i c u l a t e a nd C o n d en s ib le 9 r g a n i c E m i ss i on s . . . . . . 6-29 R e s u l t s o f EFA Te s ts o f a S o i l e r I n c i n e r a t i o nS y s t em - - T ot a l G r g a n i c E m i s s io n s ( Y e t n o d 2 5 ) a tV e n e e r 3 r y e r E x h a u s t . . . . . . . . . . . . . . . . . . 6 - 2 1 R e s u l t s o f EPA T e s ts o f B o i l 3 r I n c i n e r a t i o nS y s t e m - - T o t a l Q r g a n i c E m i s s i o n s ( Y e t h o d 2 5 ) a tV e n e e r 3 r y e r E x h a u s t . . . . . . . . . . . . . . . . . . . 5-22 R ~ s u ls o f EPA T 2 st s o f a S g i l e r I n c i n e r a t i o nS y s t e m - - T o t a l O r g a n i c E i n i s s i o n s ( M e th o d 2 5 ) a tB o i l e r E x h a u s t . . . . . . . . . . . . . . . . . . . . . -23 R e s u l t s o f EPA T? s ts o f a B o i l e r I n c i n e r s t i o nS y s t em - - To t a l O r g a n i c E m i s s i o n s ( Y e t h c d 2 5 ) a tB o i l e r E x h a u s t . . . . . . . . . . . . . . . . . . . . . 6-24 T e s t s S h ow in g E m i s s i o n R z d u c t i o n s A c h i e v e d b yL o w e r i n g D r y e r T m p e r a t u r e s . . . . . . . . . . . . . . . 6-25 Summary o f S t a t e o f 3 r e g o n R e g u l a t i o n s f g rP ly w oo d V a n u f a c t u r i n g . . . . . . . . . . . . . . . . . . 6-27 E n i s s i o ns F ro m P l y w oo d S a n de r s w i t h F r o d u c tR e c o v e r y C y c l o n e s . . . . . . . . . . . . . . . . . . . . 6-23


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L I S T OF FIGURESNumber Page

S o f t w o o d p l y \- r o o d p r o d u c t ior1 by r e g i o n . 1 9 6 0 - 1 9 8 0 2 - 8 P r o ce s s f l o w d i a g r a m f o r v e n e e r an d p l y w o odp r o d u c t i o n . . . . . . . . . . . . . . . . . . . 2 - 1 1 Two-zone 1o n gi u d i n a l - f l o w d r y e r . . . . . . . . 2-13 N e t e nd o f a st ea m- he at ed l o n y i t u d i n a l - f l o w d r y e r 2-15 Three.zone. t w e l v e - s e c t i o n j e t d r y e r . . . . . . 2-16 C ro ss s e c t i o n o f a s t ea m- he at ed j e t d r y e r . . . . 2-17 G e o r i j i a - P a c i f ic e m i s s i o n e l i m i n a t o r . . . . . . . 3-3 2ader SandA i r f i1 e r . . . . . . . . . . . . . . 3-5 '/Jood-f i r e d d r y e r s y ste m w i t h p a r t i a l i n c i n e r a ~ i o ni n a f u e l c e l l . . . . . . . . . . . . . . . . . 3-9 S.Jood.f ir e d s y ste m w i t h coinpl e t e i n c i n e r a t i o n o f d r y e re xh au st i n a f u e l c e l l . . . . . . . . . . . . . . 3 - 1 1 F a b r i c f i l t e r s y s te m f o r c o n t r o l o f s a n de rd us te m i s s i o n s . . . . . . . . . . . . . . . . . . . . . 3 - 1 5 O re go n D e p a rt m en t o f E n v i r o r i ~ n e n t a l g u a l it y blethod 7 sampl ing t r a i n . . . . . . . . . . . . . . . . . . 6 - 2 W as hi ng to n S t a t e U n i v e r s i t y ( 1 97 2 ) s a m p li n g t r a i a . 6 - 4 r r l o d i f i e d EPA M e th o d 2 5 s a l i l p l i n g t r a i n . . . . . . . 6-7 Simp1 if i e d sc he m at ic o f n o m e t h an e o r g a n i c a n a l j z e r( M e t h o d 2 5 ) . . . . . . . . . . . . . . . . . . . . 6.9Y o d i f i e d EPA M e t h od 5 X / 2 5 s a dp l i n y t r a i n . . . . . 6-1'3


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1 . 0 INTRODUCTION

T h i s d oc um en t s u mm a ri ze s i n f o r m a t i o n g a t h e r e d b y t h e U .S. E n v i r o n -m e n t a l P r o t e c t i o n A ge nc y (EPA) o n t h e c o n t r o l o f e m i s s i o n s f r o m s o f t w o o dp l y w o od m a n u f a c t u r i n g . The p r i m a r y so u r c es o f e m i s s i o n s f r o m t h i si n d u s t r y a r e v en ee r d r y e r s a nd pa n e l s an de rs . V e ne e r d r y e r s e m i t co n-d e n s i b l e a n d n o n c o nd e n s ib l e o r g a n i c c om pounds a n d m i n o r q u a n t i t i e s o fp a r t i c u l a t e m a t t e r . The r a t e o f u n c o n t r o l l e d c o n d en s i b le an d non con-d e n s i b l e o r g a n i c c ompound e mi s s io n s f r o m a v e ne e r d r y e r i s a f u n c t i o n o ft e s t m et ho d, wood c h a r a c t e r i s t i c s ( s p e c i e s , m o i s t u r e c o n t e n t , e t c . ) , a ndd r y e r o p e r a t i n g c o n d i t i o n s (t e m p e r a t u r e , s p ee d, e t c . ) . As a n e xa mp le o ft h e - m a g n i t u d e o f t o t a l o r g a n i c e m i ss i on s f r o m a p ly w oo d p l a n t , N a t i o n a lC o un c i l o f t h e P ape r I n d u s t r y f o r A i r a n d S t r e a m I m p r o ve m e n t , I n c . ,(NCASI) s t a f f m eas ure ments o f t o t a l o r g a n i c e m is s io n s f r o m u n c o n t r o l l e dS o u t h e r n p i n e v e n e e r d r y e r s s how ed a v e ra g e Me t ho d 2 5 e m i s s i o n s r a t e s o f13 .7 g/m2 as C,, 9.5-mm ba s i s ( 2 .8 l b /1 , 000 f t 2 , 0 . 3 7 5- i n . b a s i s ) o nf r e s h c u t v en ee r. F o r a r e p r e s e n t a t i v e new S o ut h er n p ly w oo d p l a n t w i t ht h r e e d r y e r s p r o d u c i n g 1 7. 2 x l o 6 m2/y r , 9.5-mm b a s i s ( 185 x l o 6 f t 2 / y r ,0 . 3 7 5- i n. b a s i s ) o f p l yw o o d, t o t a l o r g a n i c e m i s s io n s w o u l d b e 2 35 M g /y r( 25 9 t o n / y r ) . P an el sa nd er s p r od u ce p a r t i c u l a t e e m i s si o n s a t a r a t ed ep en d i ng o n t h e f i n a l p r o d u c t . A p p ro x im a te l y 1 8 t o 20 p e r c e n t o f a l ls o f t w o o d p l y w o od p r o d u c t i o n i s sa nd ed.

The i n d u s t r y i s l a r g e l y l o c a t e d i n t h e N o r t h we s t a nd S ou th . V en eerd r y e r e m is s io n s a r e c o n t r o l l e d i n some N o rt h w e st e r n S t a t e s , n o t a b l yO re go n, b y a v a r i e t y o f w e t s c ru b b i n g a nd i n c i n e r a t i o n schemes. I n t h eS ou th , w he re i n d u s t r y g ro w th i s e x pe ct ed t o c o n c e nt r a t e , a l l b u t a fe wd r y e r s a r e u n c o n t r o l l e d . P an el sa nd ers a r e c o n t r o l l e d b y f a b r i c f i l t r a -t i o n i n m os t S t a t e s , a l t h o u g h h i g h - e f f i c i e n c y c y c lo n e s may m ee t e m i s si o n ss t a n d a r d s i n some S o u t h e r n S t a t e s .


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The r e m a in d er o f t h i s r e p o r t d e t a i l s t h e s ou rc es a nd ty p e s o fe m i ss i on s f ro m t h e p ly w oo d i n d u s t r y , t h e t y p e s a nd c o s t s o f e m i s s i o n sc o n t r o l t e ch n iq u e s, e n v ir o n m en t a l i m pa c ts a s s o c i a t e d w i t h t h e s e c o n t r o lt e ch n iq u e s, and a v a i l a b l e e m i ss io n s t e s t d a ta .


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2. SOURCES AND TYPES OF EMISSIONS

2 . 1 PRODUCT CHARACTERIZATIONP ly wo od i s a p r o d u c t com posed o f l a y e r s o f w ood v e ne e r g l u e d t o g e t h e r

w i t h a n a d h e s i ve , u s u a l l y a s y n t he t ic - r- e sj -n . The g r a i n o f e a ch s u c c e s s i v el a y e r i s p l ac ed a t r i g h t a ng l e s t o g i v e t h e p r o d u c t s t r e n g t h i n tw od i r e c t i o n s . A ve ne er , o r p l y , i s a t h i n s h e e t o f wood, p e e le d o r s l i c e df r o m a l o g . S o ft wo o d p ly w oo d i s c o n s t r u c t e d u s i n g v en e er s, i n c l u d i n gt h e f a c e p l y , f ro m c o n i fe r o u s o r n e e d le b e a ri n g t r e e s . Wood spec ies usedi n s o f t w o o d p l yw o o d m a n u f a c tu r e i n c l u d e D o ug la s f i r , W h i t e f i r , hemlock ,P onde ros a p i ne , S ou t h e r n p i ne , and r edw ood . H ar dw ood v enee r d r y i n g ands a n d i n g a r e n o t c o n s i d e r e d i n t h i s d ocu me nt b e ca us e e m is s io n s f r o m t h e s ep ro c es se s a r e i n s i g n i f i c a n t com pared t o e m i s s i o n s f r om s o f t wo o d p r oc e ss e s.

S of tw oo d pl yw o od i s u se d f o r r o o f d ec ks , e x t e r i o r s h e a th i n g , p ly w oo ds i d i n g , a l l - w e a t h e r wood f o u n da t i on s , a nd ro u gh f l o o r i n g i n h ou s in gc o n s t r u c t i o n . It i s a l s o u sed i n l i g h t i n d u s t r i a l r o o f s , heavy tongue -a n d- gr oo ve c om m e rc ia l f l o o r s ys te m s, a nd f u r n i t u r e . l T h e re a r e a b o u t 50t o 6 0 d i f f e r e n t g ra d es o f s o f t w o o d p ly w oo d , a n d many m i l l s pr o du c e m oret h an one t y p e o f p l y ~ o o d . ~2 . 2 INDUSTRY PROFILE

The m a j o r i t y o f p l a n t s i n t h e s o ft wo o d p ly wo od i n d u s t r y a r e l o c a t e di n t h e P a c i f i c N o rt h w e s t (O re go n, W a sh in gt on , an d C a l i f o r n i a ) , w i t h t h es e co n d -l a rg e s t c o n c e n t r a t i o n i n t h e So ut he as t. I n 1 98 0, s o f tw o od p l y w o ~ dp r od u c t i o n t o t a l e d 1 .53 b i l l i o n m2, 9.5-mm b a s i s (1 6 .5 b i l l o n f t 2 ,3 /8 - i n . b as is ) . " f t h i s t o t a l , 0 .2 8 b i l l i o n m2 , 9.5-mm bas is ( 3 . 0b i l l i o n f t 2 , 3 / 8 - in . b a s i s ) , c o n s t i t u t e d sa nd ed p ly wo o d p r o d u c t i o n .T h i s p l yw o od p r o d u c t i o n r a t e i s a 1 6 - p e r c e n t d e c re a se f ro m t h e 1 . 8 5-b i l l i o n m2 , 9.5-mm b a s i s ( 2 0 . 0 - b i l l i o n f t 2 , 3 / 8 - in . b a s i s ) , p r o d u c t i o nr a t e o f 1 97 8. T a b l e 2 - 1 shows t h e number o f p r o d u c i n g u n i t s i n ea chS t a t e t o g e t h e r w i t h p r o d u c t i o n by S t a t e a nd r e g i o n .


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TABLE 2-1. PLYWOOD PRODUCTION BY STATE AND REGION, 1 9804( b i l l i o n m2 , 9.5-mm basis)I n d u s t ~ y r o d uc t io n P er ce n tR eg io n a nd S t a t e U n i t s (m 2 x l o9 /y r ) o f U.S. t o t a l

N o r t h w e s tOregonWashi na to n~ a l , , i , f o r n i a 0 . 0 2 9- 6 -S o u t h e a s t YL o u i s i a n aTexasA1 abamaM i s s i s s i p iA rkansasG e o r g i aN o r t h C a r o l inaS o u t h C a r o l i n aF l o r i d aV i r g i n i aOk l ahomaMary 1and

I n l a n dMontanaI d a h o

TOTAL 1. 51 5 -10 0.0 -


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I n J an ua ry 19 80 , a n e s t im a t e d 267 f a c i l i t i e s w er e m an u f a c tu r i n gs o ft w oo d p l y wo o d a nd ve ne er i n t h e c o n t i n e n t a l U n i t e d S t a t e s . O f t h i snum ber, 65 p l a n t s p r o du c e d o n l y v e ne e r, w h i l e 202 p l a n t s p ro d uc e d e i t h e rp l y w o o d a l o n e o r b o t h p l y w o o d an d ve n ee r . B y J a n u a r y 1 9 8 2, many m i l l sw e re c l o s e d , e i t h e r t e m p o r a r i l y o r pe r m an e a tl y .

The t o p f i v e f i r m s a c co un te d f o r 40 .5 p e r c e n t o f p r o d u c t i o n i n1 97 2 a n d f o r 4 7 .5 p e r c e n t 3 f p r o d u c t i o n i n 1 97 9. 3 The t o p 20 f i r m sa c c ou n t ed f o r a p p r o x i m a te l y 7 0 .9 a nd 7 5 .2 p e r c e n t o f p r o d u c t i o n i n 19 72a nd 1 97 9, r e s p e c t i v e l y , T h e r e f o r e , i n d u s t r y 1e a d e r s g a i n e d m a r k e ts h ar e l a r g e l y a t t h e expense o f s m a l l f i r m s .

M os t r e c e n t gr o w t h i n new p l a n t s h as o c c u r r e d i n t h e So uth . A l s o ,t h e a p p a r e n t i n d u s t r y t r e n d h a s be en t o w a r d g r e a t e r c a p a c i t y among newp l a n t s . C o n s eq u e nt l y, S o u t h e r n p l a n t s a r e g e n e r a l l y ne we r a nd h av el a r g e r c a p a c i t i e s t h a n do N o r t h w e s te r n p l a n t s . I n 1 97 9, a n a v er ag eN o r t h w e s t e r n p l a n t p r o d u c e d 8 . 3 6 m i 11 o n m2, 9.5-mm b a s i s (90 mi 11 o nf t 2 , 3/8- in. b a s i s ) , o f s o f t w o o d p l y w o o d . T he a v e r a g e S o u t h e a s t e r np l a n t p ro du ce d 11 .9 m i l l i o n m2, 9.5-mm b a s i s (1 2 8 m i l l i o n f t 2 , 3 / 8 - i n .b a s i s ) , o f s o f t wo o d p ly w oo d i n 19 79 .

D a ta a r e n o t a v a i l a b l e o n t h e ages o f i n d i v i d u a l p l a n t s . M os tN o r t h w e s t e r n p l a n t s a r e 30 y e a r s o l d , w he re as m o st S o u t h e a s t er n p l a n t sa r e l e s s t h a n 1 5 y e a rs o l d . P l a n t s c l o s e p e r i o d i c a l l y a nd a r e f r e -q u e n t l y r e b u i l t b ec au se o f ch an ge o f wood s u p p l y o r c ha ng e o f o w ne rs h ip .P r o d u c t io n a t s i n g l e s i t e s may c o n t in u e f o r d e c a d e s ( e . g . , t h e M c C l ea r yW a sh in gt on p l a n t was b u i l t i n 1 91 2j"r may b e t e r m i n a t e d a f t e r a f ewmon ths .

Many com pa nie s i n t h e s o f tw o o d p ly w oo d i n d u s t r y a r e v e r t i c a l l yi n t e g r a t e d . W e y er ha e us e r, C ro wn Z e l l e r b a c h , U n i o n Camp, G e o r g i a - P a c i f i c ,S ou th we st F o r e s t I n d u s t r i e s , a nd I n t e r n a t i o n a l P ap er a l l own t i m b e rs t a n d s t h a t s u p p l y l o g s f o r p l y w o o d m a n u f a c t u re . T he se c om p an ie s h a vea n ad v an t ag e o v e r f i r m s t h a t m u st p u r ch a s e t i m b e r o n t h e o pe n m a r k e tb e c a us e st um p ag e c o s t s h a v e j um p ed a l m o s t 7 5 p e r c e n t s i n c e 1 9 7 8 , t on e a r l y $ 40 0 p e r 1 ,0 00 b o a r d f e e t . S t . R e g i s , Ch am pio n, P o t l a t c h , B o i s eC ascade, L o u i s i a n a - P a c i f i c , a nd W i l l a m e t t e s u p p ly o v er h a l f t h e i r ra wm a t e r i a l n ee ds f r o m t h e i r own t i m b e r l a n d s .


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I n 19 79 , t h e s o f t w o o d p l yw o o d i n d u s t r y e m p lo ye d a p p r o x i m a t e l y46, 100 w o r k e r s . S t a t es l ea d i ng em pl oy m en t a r e O r egon, W as h i ngt on ,Te xa s, a nd L o u is i a na , a c c o u nt i n g f o r 67 p e rc e n t o f t o t a l i n d u s t r yem pl oy m en t i n 1977 . lo

Employment s t a t i s t i c s f o r t h e y e a r s 1 97 2 t h r ou g h 1 97 7 a r e g i v e n i nT a b l e 2 -2 . T he t a b l e shows t o t a l e s t a b l i s h m e n t s a nd e m pi oy e es , w ag es ,h o u r s , a nd p r o d u c t i o n w o r ke r s. I t l i s t s f i g u r e s f o r v a lu e added bym a n u f a c tu r e , m a t e r i a l s c o s t , a n d s h ip m e n t.2 . 2 . 1 M a r k e t s

A num ber o f f a c t o r s a f f e c t t h e U.S. p l y w o od m a r k e t. It appea r st h a t o v er t h e n e x t f ew y e a rs , o r i e n t e d s t r a n d b oa rd s and w a fe r bo a rd w i l lbe u se d i n c r e a s i n g l y as p ly wo od s u b s t i t u t e s . I n f a c t , i t i s e s t im a te dt h a t n on ve ne er p a n e l p r o d u c t i o n may be up t o 0 . 23 2 b i l l o n m2 , 9.5-mmb a s i s (2 .5 b i l l i o n f t 2 , 3 / 8 - in . b a s i s ) , i n t h e co mi ng y e a r s . 4

I n t e r n a t i o n a l a c t i v i t i e s m o d er a te l y i m pa c t U.S. p r o d u c t i o n . TheU n i t e d S t a t e s i m p o r t s s o f t w o o d p l yw o o d m a i n l y f r o m C anada a nd M e x i c o ,t ho u gh n o t t o an y s i g n i f i c a n t e x t e n t . S o ft wo o d s a l e s ov er se a s ac c ou n tf o r some 5 pe r c en t o f U .S . p r od uc t i o n . B ecause U .S . c om pan i es hav eg a i n e d a gr ee me nt s i n t h e g r o w i n g i n t e r n a t i o n a l m a r k e t s and be ca us ep o t e n t i a l c o m p e t i t o r s ( Sc a n d i n av i a a nd U. S . S . R. ) do n o t ha ve s u f f i c i e n twood o r p l a n t c a p a c i t y , U.S. p r o d u c t i o n s h o u ld expand i n t h e f u t u r e t os e r ve t h e e x p o r t m a rk e t .4

The p r i c i n g c f s of tw o od p ly wo cd p r o d u c t s d e p i c t s a c l a s s i c c ase o fp r i c e e l a s t i c i t y o f demand: many m ar ke t v a r i a b l e s a f f e c t t h e p r i c e o fs o f tw o o d p r o d u c t s , m a ki ng th em p r i c e s e n s i t i v e . Even a s m a l l p r i c ed e c re a se c an i n c r e a s e p r o d u c t demand, w h i c h i n t u r n f o s t e r s a n i n c r e a s -i n g l y c o m p e t i t i ve i n d u s t r y .

Demand d e t e r m i n a n t s f o r t h e s o f t w o o d p l yw o o d m a r k e t co m p r i s e av a r i e t y o f f a c t o r s , t h e p r i m a r y f a c t o r b e i n g t h e number o f f o r e c a s t e dh o u si n g s t a r t s . D u r in g t h e f o r e c a s t p e r i o d , ve ne er pa n el use i s e s t i -m a te d a t 520 m2 p e r s i n g l e - f a m i l y u n i t a nd 300 m2 p e r m u l t i f a m i l y u n i t .T h e s e e s t i m a t e s r e f l e c t t h e e x p e c t a t i o n t h a t new use s l i k e wood fo u nd a -t i o n s a nd s t r u c t u r a l p an el f l o o r s w i l l r e p la c e c o nc re t e w a l l s and s l a bf l o o r s . These new use s w i l l o f f s e t l o s t p ly wo od use r e s u l t i n g fr om t h e


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---T A B L E 2-2. EMPLOYMENT STA TIST ICS --SO FTW OOD VENEER AND PLYWOOD"'

- .~..- - - . . . . .~ - .- . ~.-~.. . -. -. .All establishments

With 20 -ll employees Production workers Value Cost of Value of employees added by materials shipments

Yearb companiesC Total or more Number Payroll Number HoursWages manufacture ( $ mil- ( $ mil-

(No. ) (No.) (NO. ) (1 .000 's ) ( $ mil lions) (1 .000 's ) (alllions) ($ millions) ( $ millions) lions) lions)(S millions) 1972 Census 121 232 225 43.7 403.6 39.9 85.3 356.5 935.4 1,071.3 2,011 .5

1974 ASH (NA) (NA) (HA) 42 .8 421 .1 38 .5 78 . 1 363 .3 832 .0 1 ,299 .8 2 .123 .81975 ASH (NA) (NA) (NA) 41 .1 438 .6 36 .7 75 .0 377 .5 850 .3 1 ,386 .5 2 ,243 .51976 ASH (NA) (NA) (NA) 45 .0 537 .8 40 .5 84 .5 468 .0 1.304.2 1 , 8 8 0 . 5 3 , 1 6 4 . 11917 Census 129 256 224 46 .2 634 .6 41 .9 89 .0 556 .9 1 ,583 .7 2 ,23 1 .1 3 ,804 .8

~-- ~- - - - - -.--a~ndustrywas defined or redefi~~edor 1972 Census of Manufacturers, so data are available only for years shown.

annual survey of manufacturers (ASH) years, data ar e estimates based on a representative sample of establishments canvass ed annually and may I differ from a canvass of all establishments.

CFor the census, a company is defined as a business organization consisting of one establishment or more under co mmon owne rshi p or control.


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t r e n d t o w a r d c o n s t r u c t i n g s m a l l e r u n i t s w i t h m ore common w a l l s . M o b i l ehomes a dd t o t h e r e s i d e n t i a l v olu me . S t r u c t u r a l p a n el u se i s e x p e ct e dt o g row i n t h i s m a r k e t as t h e t r e n d t ow a r d more d ou bl e- wi de u n i t s c on -t i n u e s . Use p e r u n i t i s e x pe ct ed t o i n c r e as e f r om 38 m2 t o 80 m2 o n t h eave rage .

The s e c o n d - l ar g e s t m a r k et f o r s t r u c t u r a l p a n e l s i s t h e h omeownerm ar ke t, a bo ut t w o - t h i r d s o f w hi ch i s f o r s t r u c t u r a l a d d i t i o n s , a l t e r a -t i o n s , a nd p r o p e r t y i mp ro ve m en ts . T h i s c a t e g o r y i n c l u d e s g a r ag e s ,s t o r a g e s he ds , p r i v a c y s c r e e n in g , p a t i o s , a nd p l a n t e r s . The r e m a in d e ro f t h e homeowner m a r k e t i n c l u d e s s u c h m i s c e l l a n e o u s u se s a s f u r n i t u r e ,s h e l v i n g , t o y s , games, p e t s h e l t e r s , t e m p or a r y c l o s u r e s , p a n e l i n g , a nd ah o s t o f o t h e r a p p l i c a t i o n s . The homeowner m a r k e t i s e x p ec t e d t o c o n t i n u et o i n c re a s e a t a 2- t o 3 -p er ce nt r a t e each y e a r, r e f l e c t i n g p o p u l a t i o ng r ow t h, c o n t i n ue d , s t r o n g u p g ra d i ng o f h ou se s, an d a d d i t i o n a l a c t i v i t y .

D i ve r s e i n d u s t r i a l uses c o n s t i t u t e t h e t h i r d - l a r g e s t s t r u c t u r a lp a ne l m a r k et . The t wo l a r g e s t us e a re a s a r e m a t e r i a l s h a n d l i n g ( p a l l e t s ,b i n s , c r a t e s , and i n d u s t r i a l s h e l v in g ) a nd t r a n s p o r t a t i o n ( t r u c k b o d i es ,bus f l o o r s , r a i l c a r l i n e r s , and r e c r e a t i o n a l v e h i c le s ) . A l l -v e n ee rs t r u c t u r a l p a n el s do m in at e t h e i n d u s t r i a l m a r k et s and a r e e x pe c te d t oc o n t i n ue t o do so, e s p e c i a l l y i n m a t e r i a l s h a n d l in g and t r a n s p o r t a t i o nequ ipmen t a reas .

N o n r e s i de n t i a l co ns um pt jo n c o n s t i t u t e s t h e f o u r t h - l a r g e s t s t r u c t u r a lp an el m a r ke t . P ly wo od u sed i n b u i l d i n g c o n s t r u c t i o n an d i n c o n c r e tef o rm i n g a cc ou nt s f o r 90 p e r c e n t o f t h e n o n r e s i d e n t i a l m ar ke t. A u x i l i a r ya p p l i c a t i o n ; i n c l u d e s i g n s , b a r r i c a d e s , w o rk h or se s , b e nc h s h o r i n g ,r e t a i n i n g w a l l s , a nd h ig hw a y s ou nd b a r r i e r s . A p p l i c a t i o n s s uc h a s s ou ndb a r r i e r s and r e t a i n i n g w a l l s have p o t e n t i a l f o r s u b s t a n t i a l g ro wt h.O v e r a l l , n o n r e s i d e n t i a l u se s a r e f o r e c a s t t o expand g r a d u a l l y a t 1 t o 2p e r c e n t p e r y e a r .2.3 TRENDS

The s o f t w o od p ly w oo d i n d u s t r y h as s hown a h i g h l y v a r i a b l e b u tc o n s i s t e n t l y i n c r e a s i n g p r o d u c t i o n p a t t e r n o v e r t h e p a s t t h r e e d ecades.Some p r o d u c t l i n e s r e c e n t l y h av e e xp an de d w h i l e o t h e r s h a v e n e a r l yd i s ap p e ar e d b ec au se o f c o m p e t i t i o n f r o m s u b s t i t u t e s o r c h a ng i n g co ns um ert a s t e s .


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P r o d u c t i o n t r e n d s o v e r t h e l a s t 20 y ea r s a r e shown i n F i g u r e 2 -1 ,w h i c h shows s o ft w o o d p l yw o o d p r o d u c t i o n b y r e g i o n . N o t e t h a t S o u t h e rnp r o d u c t i o n i n cr e as e d fr om z er o t o 45 .3 p e r c e n t o f t h e n a t i o n a l t o t a ld u r i n g t h a t t i m e . U n t i l 1 98 1, S o ut he rn p r o d u c t i o n had i n c r ea s e d e v e r yy e a r e x c e p t f o r 1 97 4. W e st er n an d i n l a n d p r o d u c t i o n g e n e r a l l y hasf l u c t u a t e d a ro un d a b ase l e v e l , i n c r e a s i n g l e s s c o n s i s t e n t l y t h a n S o ut he rnp r o d u c t i o n h a s .

W h i l e s o f t w oo d p l yw o o d p r o d u c t i o n has i n c r e a s e d g r a d u a l l y o v e r t h ep a s t d e c a d e , i t has n o t m at ch ed t h e 1 1 - p e r c en t a nn u al r a t e e s t a b l i s h e df r o m 19 45 t o 1 96 8. D u r i n g t h e p a s t d ec ad e, t h e i n d u s t r y ha s e xp an de dp r o d u c t i o n by a d d i n g o r r e p l a c i n g v en ee r d r y e rs i n e x i s t i n g p l a n t s andb y b u i l d i n g new g r e e n f i e l d p l a n t s . Because d r y i n g c a p a c i t y i s a l i m i t i n gf a c t o r i n many p l a n t s , a d d i t i o n a l d r y i n g c a p a c i t y has a u t o m a t i c a l l yi n c r e a s e d t o t a l p r o d u c t i o n c a p a c i t y . M os t o f t h e new p l a n t s ha ve be enc o n s t r u c t e d i n t h e S ou th ea st .

The r a p i d l y i n c r e a s i n g t i m b e r a nd p ly wo od p r o d u c t i o n i n t h e S o ut he as ta nd S ou th sh o u ld c o n t in u e t o i n c r e a s e w e l l i n t o t h e 1 9 8 0 ' s . T im b2 rs u p p l y has b ee n a p r i m a r y f a c t o r i n de ve lo pm en t o f t h e S o u th e rn p i n ep ly w oo d i n d u s t r y . B eca use t h e y ha ve b ee n a s s u r ed t i m b e r a v a i l a b i l i t yf r o m p r i v a t e h o l d e r s o f t i m b e r l a n d , many f i r m s h av e ex pa nd ed c a p a c i t y b yb u i l d i n g m i l l s i n th e S ou th r a t h e r t h a n b y i n c re a s in g c a p a c i t y i n ar e g i o n c o n t r o l l e d b y p u b l i c t i m b e r management.

I n 1 98 0 a nd 1 98 1, p r o d u c e r s c u t p r i c e s t o move wood, a s t r a t e g yt h a t p r ov e d o n l y m a r g i n a l l y s u c c e ss f u l . The u n d e r l y i n g p ro bl em i s ad e p r e s se d h o u s i n g m a r k e t , w h i c h i n 1 9 8 1 c l o s e d many W e st e rn m i l l s , somep e r m a n e n t l y .

Many p l a n t s a r e now o p e r a t i n g i n t h e r e d . Some a r e a b l e t o c o n t i n u eo p e r a t i n g o n l y w i t h p a r e n t company s u b s i d i e s t h r o ug h t h e c u r r e n t r e c e ss i o n .T h i s s u b s i d i z a t i o n i s p a r t l y d ue t o t h e f a c t t h a t some co mpa nies n eedwood c h i p s f r o m t h e i r p ly wo od m i l l s as r aw m a t e r i a l s f o r t h e i r p ap e rm i l l s .

E n er gy a nd m i n e r a l r e s o u r c e s h o r t a g e s c o u l d b e c o n s i d e r e d a po t e n -t i a l boon t o t h e p ly wo od i n d u s t r y . P lywood comes f rom a rene wab l er e s o u r c e an d c a n be m a n u fa c t u re d w i t h f a r l e s s e n e r gy t h a n c a n m o sto t h e r b u i l d i n g m a te r ia l s .


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The pl yw o od i n d u s t r y t r a d i t i o n a l l y has u se d s h o r t - t e r m m a r k e tc o n d i t i o n s a nd p r o d u c t i o n c o s t s as p r i n c i p a l f a c t o r s i,n d e c i d i n g t ob u i l d new p l a n t s o r t o c l o s e e x i s t i n g o nes. As a n e t e f f e c t , r a p i dp l a n t t u r n o v e r s h ave h ad a m a j o r i m p a c t o n t h e number o f new p l a n t s .A l s o , m os t p l a n t s c l o s e p e r i o d i c a l l y b eca use o f wood s u p p l y, p r o d u c tl i n e , o r o wn er c ha ng es .

How ever, t h e s i z e o f i n d i v i d u a l p l a n t s has i n c r e a s e d o v e r t h e p a s tfe w y e a r s , e s p e c i a l l y f o r new, i n t e g r a t e d s o ft w o od p l yw o o d p l a n t s .I n c o r p o r a t i o n o f p l yw oo d o r v en ee r f a c i l i t i e s i n t o t o t a l wood p r o d u c t i o ncom plexes ( wh ic h i s o c c u r r i n g i n l a r g e f o r e s t i n d u s t r y c o r p or a t io n s )w i l l be r e f l e c t e d i n i n c r ea s e d s t a b i l i t y and c o nt in u ed u p gr ad in g ofi n d i v i d u a l p l a n t s . I t i s e s t i m a te d t h a t e x i s t i n g v en ee r d r y e r s u n de rg om a jo r r e c o n s t r u c t i o n o r m o d i f i c a t i o n e v e r y 1 5 y e a rs . l 1 T h e r e a r ep r e s e n t l y no known p l a n s f o r new p l y w o o d p l a n t s , t h o u g h on ce r e c o v e r yf r o m t h e h o u s i n g s lu mp commences, t h i s s i t u a t i o n m i g h t c ha ng e.

E x i s t i n g s o ft wo od p lyw oo d c a p a c i t y a t 2 .2 7 b i l l o n m2, 9.5-mm basis( 2 4 . 4 b i l l o n f t 2 , 3 /8 - i n . b a s i s ) , i s s u f f i c i e n t t o meet i n c r e as e ds o f tw o o d p l y w o o d demand t h r o u g h 1 98 6, w h i c h i s p r e d i c t e d t o b e 1 . 89m i l l i o n m2 , 9.5-mm b a s i s ( 2 0. 3 b i l l i o n f t 2 , 3 / 8 - i n . b a s i ~ ) . ~ owever ,p a s t t r e nd s i n d i c a t e t h a t new p l a n t s w i l l be b u i l t t o r e p l a c e p l a n t st h a t c l o s e o r t o s ee k a l a r g e r m a r ke t sh a re b y o f f e r i n g a mo re ec cn -o m i c a l l y p r o du ce d p r o d u c t . From 1 97 7 t o 1 97 9, p r o d u c t i o n i n t h e S o u thi n c r e a s e d 1 2 p e r c e n t , where i t a p p e ar s m o st new g r o w t h i n t h e p l y w o o di n d u s t r y w i l l o c c ur . A nn ua l pl yw o od p r o d u c t i o n may r e a ch 2 . 4 b i l l o nm 2 , 9.5-mm b a s i s ( 26 . 5 b i l l i o n f t 2 , 0 . 35 - i n . ba s i s ) , by 1995 . T he abov ep r e d i c t i o n s m us t be u s ed w i t h c a u t i o n b eca us e o f t h e c u r r e n t e co no mics lump.2 . 4 PROCESSES AND THEIR EMISSIONS

F o u r pr o ce s se s u s ed t o p r o d u ce p ly w o od a r e l i s t e d b el ow :G reen p r o c e ss - - lo g c o n d i t i o n i n g , f o l l o w e d b y p e e l i n g i n t og r een v enee r ;V e n e e r d r y i n g ;V en ee r p a t c h i n g a nd g r a d i n g , l a y u p an d g l u i n g , a nd p r e s s i n g t omake p lywo od; andS i z i n g and f i n i s h i n g o f t h e p lyw oo d.


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F i g u r e 2 -2 i s a g e n e ra l i z e d f l o w c h a r t f o r t h e s e p ro ce ss e s.2 .4 .1 Green P rocesses

C o n t i n u a l l o w - l e v e l e m i ss i on s o f v o l a t i l e wood co mp on en ts o c c u rt h r o u g h o u t t h e l i v e s o f s o f tw o o d t r e e s . These em i s si o ns c o n t i n u e whent h e l i v e t r e e s a r e c u t an d d u r i n g t h e ve ne er d r y i n g p ro ce ss ; t h e e m i s s i onr a t e i n c r e a s e s as te m p e r a tu r e a nd wood s u r f a c e a r e a i n c r e a s e . V o l a t i l ec o mp o n e n ts - - p r ima r i l y t e rp e n e s - -a re e s t im a te d a t 20 g/m2, 9.5-mm b a s i s(4 l b /1 ,0 0 0 f t 2 , 0 . 3 7 5 - i n . b a s i s ) , o f p r o d u c t f o r f r e s h l y c u t So ut he rnp i n e s . l2By t h e t i m e g re e n v e ne er h as be en p re p a r e d f o r d r y i n g , t h i sco mp on en t ha s d e cr ea s ed s i g n i f i c a n t l y . M os t s t u d i e s o f t e r p e n e l o s sf ro m wood i n d i c a t e r a p i d l o s s f r om l o g s o r t h i n s h ee ts o f wood w i t h i n 1t o 8 weeks a f t e r c u t t i n g . l34l5G e o r g i a - P a c i f i c e x pe r ie n ce i n d i c a t e st h a t l o g s l o s e a p pr o xi m a te l y 6 p e r ce n t o f t o t a l w e i g h t i n wood m o i s t u r ed u r i n g a t y p i c a l 3-week l ~ gt or ag e p e r i od . l6

A f t e r d e l i v e r y t o a w es t co a s t p ly wo od f a c i l i t y , t h e l o g s a res t o r e d i n a p on d o r p i l e d on a pr e pa r ed s u r f a c e c a l l e d a c o l d d eck. Thel a t t e r s t o r a g e me th od r e q u i r e s w a t e r s p r a y i n g i n warm p e r i o d s t o p r e v e n tl o g d e t e r i o r a t i o n . I n t h e S ou th , l c g s u s u a l l y come d i r e c t l y f r om t h ewoods t o an o pe n l o g y a r d . Pond s t o r a g e i s a l m o s t n e v e r us ed , a nd w a t e rs p r ay i n g i s o n l y used i f p r o l on g e d s t o ra g e i s a n t i c i p a t e d . N e x t, l o g sa r e d eb ar ke d and c u t i n t o s p e c i f i c a l l y s i z e d b l o c ks . The b a r k i s r ec ov -e r e d and u se d f o r f u e l .

The n e x t o p e r a t i on a t most p l a n t s i s l o g c o n d i t i o n i n g - - t r e a t i n g t h el o g s w i t h h e a t an d m o i s t u r e - - f o r w h i c h h o t w a t e r v a t s o r s p r a y cha mb ersa re used . A t some m i l l s , s of tw o od s a r e p e e l e d c o l d w i t h o u t s uc h c on -d i i c n i ng .

V en ee r c an be c u t fr o m l o g s by s e v e r a l m etho ds. E s s e n t i a l l y , a l ls o f tw o od ve ne er i s c u t b y p e e l i n g o r r o t a r y c u t t i n g . O the r me thods a reused p r i m a r i l y f o r d e c o r a t i v e c u t s f o r f a c e v en ee r and f o r s p e c i a le f f e c t s w i t h c e r t a i n woods. S o ft wo od v en ee r i s c u t t o t h i c kn e s s e sr a n g i n g fr o m 2. 5 t o 8 . 0 mm ( 0 . 1 t o 0.313 i n . ) .

A f t e r t h e v en ee r i s p e el ed , i t i s b r o u g h t a s a s e m ic o nt i nu o u sr i b b o n t hr o ug h a u to m a ti c c l i p p e r s and c u t t o s i z e b e f o r e d r y i n g . Thesem achine s a u t o m a t i c a l l y d e t e c t and c l i p o u t u n ac c ep t ab l e s e c t i o n s o f


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- -

4

LOGS TOR A GE - D E B A R K E i l LOGC O N D I T I O N E R

I i

V E N E E R VENEERC U T i E R D R I E R

V E N E E R O P E R A T I O N

, # +- VENEERP R E P A R A TlON ;r G L U EL I N E =. PRESS - F I N I S H I N GC .. i

P L Y W O O D O P E R A T I O N

Figure 2 -2 . Process flow diagram for veneer and plywood production.


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v enee r . The g r ee n v en e er i s t h e n s o r t e d a c c o r d i n g t o s i z e , wood s p e c i e s ,and v enee r g r ade and w he t he r i t i s h ea rt wo od o r sapwood. T h i s s o r t i n gi s n e ce ss ar y b e f o r e t h e v en ee r c an be d r i e d b eca use d i f f e r e n t t y p e s o fwood r e q u i r e d i f f e r e n t d r y i n g c o n d i t i o n s . S o r t i n g i s th e l a s t s t e pb e f o r e d r y i n g .

B y p ro d u ct s o f v en e er c u t t i n g a r e l o g c o r e s , wood c h i p s , a nd ve ne ers cr a ps s u i t a b l e o n l y f o r c h i p p i n g . C onveya nce o f co a r se m a t e r i a l l e a d st o n e g l i g i b l e a i r e m is s i on s , w h i l e c onveya nce o f f i n e m a t e r i a l c an l e a dt o p a r t i c u l a t e e m is si on s.2.4 .2 V e n e e r D r y i n g

F r e s h l y c u t v e ne er m us t b e d r i e d b e f o r e i t c a n b e g l u e d a n d p r e s s e di n t o p l y w o o d . A v en ee r d r y e r i s a h ea t ed chamber w i t h l a y e r s o f r o l l s( t y p i c a l l y f ou r t o e i g h t ) t o c a r r y t h e venee r . H ea t t r a n s f e r r e d t o t h ewood b y h o t gase s c i r c u l a t i n g i n t h e d r y e r c a use s t h e v en ee r t o d r y t o al ow m o i s t u re c o n t e n t . T h is f i n a l m o is t u r e c o n t e n t i s t y p i c a l l y 2 t o 5p e r c e n t f o r Doug1 as f i r s a nd 3 t o 8 p e r c e n t f o r S o u t he r n p i n e s . l 7

Two me th od s o f h e a t i n g ve n e er d r y e r s a r e i n d i r e c t ( st ea m ) a ndd i r e c t he a t. W i t h steam h e at , t h e d r y e r i s se p ar a te fr om t h e b o i l e r ,w h i ch p ro du ce s s te am t o h e at t h e i n t e r n a l c o i l s i n c o n t ac t w i t h d r y e ra i r . W i t h d i r e c t h e a t , h o t co m bu s ti on g ase s p r o v i d e t h e e n e r gy n ece s-s ar y t o d r y t h e venee r . D i r e c t - f i r e d d r y e r s a r e f ue l e d w i t h e i t h e r gaso r wood. I n g a s - f i r e d d r y e r s , c om b us ti on c c cu r s a t a b u r ne r i n s i d e t h ed r y e r , a nd t h e he a t ed a i r i s c i r c u l a t e d t o t h e ve ne er w i t h f an s. I nw o o d - f i r e d d r y e r s , a i r i s h e a t ed o u t s i d e t h e d r y e r b y co mb us ti on o f woodf u e l . Com bust ion g ases a r e m ix ed w i t h r e c i r c u l a t i n g d r y e r a i r i n ab l e n d bo x and t r a n s p o r t e d i n t o t h e d r y e r .

D r y er s a r e a l s o c h a r a c t e r i z e d b y t h e m etho d u se d t o c i r c u l a t e h o ta i r t o t h e v en ee r s he ets . L o n g i t u d i n a l - f l o w d r y e r s may ha ve o ne t ot h r e e zo ne s; a t wo -z on e l o n g i t u d i n a l - f l o w d r y e r i s shown i n F i g u r e 2-3 .A zone i s t h e p o r t i o n o f a d r y e r t h a t has a s e l f - co n t a i n ed a i r c i r c u l a -t i o n sy ste m, a s shown i n F i g u r e 2-4; a i r c i r c u l a t e s t h ro ug h a l o n g i -t u d i n a l z on e p a r a l l e l t o ve n e er movement. The a i r i s moved b y c en -t r i f u g a l f an s l o c a t e d a t one e nd o f t h e zone. I n a s t e a m - h e a t e d l o n g i -t u d i n a l d r y e r , a i r f l o w s p a s t s team c o i l s i n t h e u pp er p len um, t h ro u g h a


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d e l i v e r y m a n i f o l d a t t h e e nd o f t h e z one , a nd down i n t o t h e v a r i o u sd ec ks c o n t a i n i n g m o v i n g ve n ee r . l8 The a i r i s c o l l e c t e d i n a no th erm a n i f o l d a t t h e o p p o s i t e end o f t h e zone b e f o r e i t r e a c h e s t h e c e n -t r i f u g a l f an s. Steam c o i l s a l s o a re i n s t a l l e d among t h e ve ne er de ck s i nt h e d r y i n g p o r t i o n o f t h e d r y e r. I n m ost d i r e c t - h e a te d s ys te ms , i n s t e a do f stea m c o i l s , h o t g as es g e n e r at e d o u t s i d e t h e d r y e r s u p p l y t h e r e q u i r e dh e a t . I n t h e g a s - f i r e d d r y e rs c u r r e n t l y used , a gas b u r n e r l o c a t e d ont h e u p p e r p l e n u m s u p p l i e s h e a t .

Ove r 90 p e r ce n t o f t h e new d r y er s i n s t a l l e d i n t h e l a s t 5 y e a r s a r ej e t- im p i ng m e nt - t y pe d r y e r s ( j e t d r y e r s ) . l g 20 F i g u r e 2 - 5 s how s a t h r e e -zone j e t d r y e r , w here h o t a i r i s d i r e c t e d o n t o t h e ve ne er s u r f a c e t h ro u ghj e t s o r h o l es i n h o r i z o n t a l plenum s. The j e t s o f h o t a i r e f f e c t i v e l yt r a n s f e r m o i s t u r e f r o m t h e wocd b y d i s t u r b i n g b ou nd ar y l a y e r s o n t h ev e n ee r s u r f a c e . T he se d r y e r s g e n e r a l l y ha ve h i g h e r g r e e n e nd t e m p e r a t u r e sa nd m ore c o n t r o l zo ne s t h a n do l o n g i t u d i n a l d r y e r s . J e t d r y e r s may b ed i r e c t f i r e d o r steam h ea te d. F i g u r e 2- 6 shows a c r o s s s e c t i o n o f as tea m-h eated j e t d r ye r . I n a j e t d r y e r , o ne s i d e o f t h e u n i t i s un de rp o s i t i v e p re ss ur e. The c o n d i t i o n o f d o or s e a l s on t h i s s i d e o f t h ed r y e r p a r t i a l l y d et er mi ne s t h e e x t e n t o f f u g i t i v e e m i ss io ns . A l l d r y e rsa r e e qu ip pe d w i t h b a f f l e s a t e ach end t o m i n i m iz e i n f i l t r a t i o n o r le ak ag ew h i l e a l l o w i n g v e n e e r m o v e m e n t .

E m is s i on s f r om d r y e r s t a c ks v a r y a c c o r d i n g t o d r y e r t y p e . Some o ft h e e m i s s i o n s f r o m g a s - f i r e d d r y e r s a r e u n b u rn e d m eth an e a nd o t h e r1ow-mol ec u l a r -w e i gh t hyd roca rbons . 2 1 B e c a u s e t h e y e m i t c o m b u s t i o ngases, w o o d - f i r e d d r y e r s may e m i t m ore o r g a n i c s t h a n do g a s - f i r e d a nds t ea m - h ea t ed v e n e e r d r y e r s . H ow e ve r, a w o o d - f i r e d d r y e r may h a ve f e w e ro v e r a l l o r g a n i c e m i s s i o n s t h a n a st ea m -h e at ed v e ne e r d r y e r an d t h ea s s o c i a t e d w o o d - f i r e d b o i l e r do b ec au se some d r y e r o r g a n i c s may bed e s t ro y e d b y h i g h t e m pe r at u re s i n t h e b l e n d bo x o r c om b us t i on u n i t .D r ye r e m is s i on s a l s o v a r y a c c o r d i n g t o t y p e o f wood i n t h e d r y e r . F o rexample, on t h e b a s i s o f mass e m is s io n s p e r p r o d u c t i o n u n i t , d r y i n gP on de ro sa p i n e v e ne e r may y i e l d o v e r t w i c e t h e e m i ss i on s f r o m d r y i n gDoug1 as f ir veneer .


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STACKM O T O R

C E N T R IF U G A L F A NB A N K O FF I N N E D -TEAM AIR FLOWCOl LS

NOTE: No scale

Figure 2-6. Cross section of a steam-heated jet dryer.


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m i x t u r e c o n s i s t s o f compounds o f h i g h e r m o l e c u l a r w e i g h t s t h a n t h em o no te rp e ne s. The compound g r ou p s i d e n t i f i e d i n c l u d e r e s i n a c i d s( n o t a b ly a b i e t i c ) , f a t t y a c i d s , and n e u t r a l s es qu i - and d i - te r p e n ecom pou nd s, a1 1 o f w h i c h h a ve a t l e a s t 1 5 c a r b o n a to ms . 21 26 D e t a i l e dg as c hr om a to g ra p h- ma ss s p e c t r o m e t e r a n a l y s e s o f c o n d e n s i b l e o r g a n i ce m i s s i o n s fr o m s e v e r a l w ood s p e c i e s a r e a v a i l a b l e . 26 The re1a t i v ea bu nda nce o f v a po r /a e r o so l f r a c t i o n s i n d r y e r e m is s i on s v a r i e s a c c o r d i n gt o wood t y p e b u t a l s o depends on m eas ur em ent t ec hn i qu e . 21 26

E m is s i on s r a t e d a t a f o r v en e er d r y e r s a r e su mm arize d i n C h a pt e r 6.A t l e a s t f o u r d i f f e r e n t t e s t m ethods h ave been use d t o q u a n t i f y d r y e re m i s s i o n s , a nd t h e r e s u l t i n g d a t a a r e n o t a lw a ys c o m pa r ab l e b ec au se o fd i f f e r e n c e s i n p h y s i c a l c o n f i g u r a t i o n s , c o nd e ns er t e m p e ra t u re s , anda n a l y t i c a l sch em es. C h a p t e r 6 c o n t a in s a d e s c r i p t i o n o f t e s t m etho dst h a t i s u s e f u l i n i n t e r p r e t i n g t h e ve ne er d r y e r e m is s i on s d a t a be low .E m i s si o n s v a r y f r o m d r y e r t o d r y e r . W i t h t h e same t e s t me th od ( Or eg onM et ho d 7 ) , c o n d e n s i b l e e m i s s i o n s f o r D o u gl as f i r a lone have been measureda t f r o m 1 . 3 t o 1 4 g/m 2, 9.5-mm b a s i s ( 0 . 2 6 t o 2 .8 6 l b /1 , 0 0 0 f t 2 , 0 . 3 7 5 - i n .b a s i s ) a t d i f f e r e n t s te am -h ea te d d r y e r s .

L i m i t e d s a m p l i n g b y W a s hi n gt o n S t a t e U n i v e r s i t y (WSU) i n d i c a t e st h a t t h e n o n c on d e ns ib l e f r a c t i o n e q u a l s o r e xce ed s t h e c o n d e n s i b l ef r a c t i o n o f e m is s i o ns f ro m D o ug la s f i r s . The s t u d y s t r o n g l y s ug g es tst h a t n o n c o nd e n s ib l e e m i s s io n s m ake up 8 0 p e r c e n t o f S o u t he r n p i n ee m i s s i o n s . 26 An e x t e n s i v e 1 9 7 2 s t u d y b y WSU f o u n d D o u g l a s f i r conden-s i b l e e m i ss i o n s t o a ve r a g e a p p r o x i m a t e l y 4 . 4 g /m2, 9.5-mm b a s i s ( 0 . 91b/1,000 f t 2 , 0 . 375 - i n. ba s i s ) . N oncondens i b l e em i s s i o ns f r om D oug l asf i r s w ere r e p o r t e d t o be much lo w e r, b u t c a l c u l a t i o n e r r o r s w ere l a t e rd i s c o v e r e d . C o r r e c t e d , n o n c o n d e n s i b l e D o u gl a s f i r e m i s s i o n s f r o m t h e1972 s tu dy average 2 . 0 ( sapwood) t o 4 .0 (hear two od) g/m2, 9.5-mm b a s i s( 0 . 4 t o 0 .8 l b /1 , 00 0 f t 2 , 0 . 3 7 5 -i n . b a s i s ) . 2 7 C o n d e n si b le e m i s s i o n sf r om S ou t he r n p i n e s a r e e s t i m a t e d f ro m t h i s r e p o r t t o b e a p p r o x i m a t e ly4.0 g/m2, 9.5-mm ba s i s (0 .8 lb /1, 00 0 f t 2 , 0 . 375 - i n . bas i s ) . N oncon-d e ns i b l e S o u t h e r n p i n e e m i s s i o n s a v e ra g e d a p p r o x i m a t e l y 11g/m2, 9.5-mmb a s i s ( 2 . 3 l b /1 , 0 0 0 f t 2 , 0 .3 75 - i n. b a s i s ) , a f t e r c o r r e c t i o n s f o r c a l -c u l a t i o n e r r o r s . 27 Thus, t h e r a t i o o f n on co nd en si b l e t o c o n d en s ib l e


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e mi ss io ns c a l c u l a t e d f r o m t h e 1972 WSU s t ud y d a t a a r e i n l i n e w i t h t ho ser e p o r t e d i n t h e 1 9 8 1 WSU r e p o r t . E x a ct ag re em e nt w o u l d n o t b e ex p e c te db ec au se o f d i f f e r e n c e s i n t e s t m etho ds ( s e e C h a pt e r 6) .2 .4 .3 Veneer P r ep ar a t io n , Layup , and G I u i n g

P ly w oo d c o n s i s t s o f s h e e t s o f v e n e er b o nd ed b y l a y e r s o f g l u e. D ryv en e er i s i n sp e c t e d , c l i p p e d , a nd s p l i c e d as ne ed ed . S te ps i n t h e l a yu pp r o c es s a r e v e ne er p r e p a r a t i o n , l a y u p o r g l u i n g , a n d p r e s s i n g . K n oth o l e s a r e p l u g g ed , a nd t h e v en e er i s r e g r a d e d as n e ce s sa r y t o p r e p a r es h ee t s f o r l a y u p .

D i f f e r e n t p ly wo od pr o du c ts r e q u i r e d i f f e r e n t g l ue s t o bond t h eveneer shee ts . App rox i ma te ly 98 pe rc en t o f t h e so f twood p-ro-duced i n t h i s c o u n t r y i s m r e s i n s .

G lu e i s a p p l i e d t o t h e p ly wo od , w h ic h i s moved i n l o o s e l a y e r s t ot h e p r e s s i n g a r e a. Many g l u e s m u s t s t a n d f o r a f e w m i n u t e s b e f o r ep r e s s i n g . * ~ n u t e s , d e pe n di ng on t h e p a n e lt h i c k n e s s . P h e n o l -f o r m a ld e h y d e g l u e s a r e s te am p r e s s e d a t t e m p e r a t u r e sra n g in g f r o m 13 2' t o 174' C a nd a t p r e s s u r e s up t o 1 ,0 3 0 kPa ( 15 0 p s i ) . 2 9D u r i n g p r e s s i n g a nd when t h e p re s s e s a re r e l e a s e d , some ga se ou s o r g a n i c smay b e e m i t t e d f r o m u n re a c te d mon omers. T he se f u g i t i v e e m is s io n s h a vebeen c o ns id e re d o n l y i n t er ms o f t h e i r i n - p l a n t e f f e c t s . T h e i r p re se nc er e q u i r e s a de qu ate v e n t i n g t o p r o t e c t w o rk er h e a l t h and t o e l i m i n a t eo d o rs .2 . 4 . 4 P ly wo od F i n i s h i n g

The l a s t s t e p i n pl yw oo d p r e p a r a t i o n i s t r im m i ng a nd f i n i s h i n g .The pl y wo o d i s t r im m e d b y s t a t i o n a r y c i r c u l a r s aw s, w h i c h re mo ve up t o25 mm (1 n . ) o n ea ch s i d e t o p r o d u c e e ve n- ed ge d s h e e ts . Then thep lywoo d she e ts may be sanded on one o r bo th fa ce s , depend ing on th ef i n a l p ro d u c t. O n ly 1 8 t o 20 p e r c e n t o f a l l pl yw o od i s sanded. D u r i n gs a n d in g , t h e s h e e ts move o n a c o n v e y o r t h ro u g h e n c lo s e d a u to m a t i c s a n d e rs,w h ic h a r e c l e a r e d c o n t i n u o u s l y o f s a nd e rd u st b y pn e um a ti c c o l l e c t o r sl o c a te d ab ov e a n d b e lo w th e p l y w oo d .

M i l l s may p ro du ce one o r s e v e r a l g r ad es o r c l a s s i f i c a t i o n s o fp l y w o o d; t h e amou nt o f p lywood sanded v a r ie s f rom none a t some p l a n t s t ot h e e n t i r e p r o d u c t i o n a t o t h e rs . The de p th o f c u t , o r amount o f m a t e r i a l


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sa nd ed f r o m e a ch pl yw o o d f a c e , v a r i e s w i d e l y w i t h p r o d u c t . D u s t f r o ms a n d in g an d t r i m m i n g o p e r a t i o n s i s t r a n s f e r r e d b y p n e u ma ti c s ys te ms t oc yc lo n e c o l l e c t o r s , i n a d d i t i o n t o w h ic h many p l a n t s have i n s t a l l e dbaghouses . S a n d e r d u s t a n d s a w d u s t a r e v a l u a b l e b y p r o d u c t s a n d a r e u s e das f u e l f o r b o i l e r s o r d i r e c t - f i r e d c o mb us t io n u n i t s .2 . 4 . 5 T e c hn o l o g i c a l C hanges

A l t h ou g h D ou gla s f i r s t r a d i t i o n a l l y h ave been use d i n so f t w oo dp l yw o o d m a n u f ac t u re , t e c h n o l o g i c a l i n n o v a t i o n s h a ve a l l o w e d t h e us e o fo t h e r so f tw o o ds : h em lo ck s, s p r u c e s, W h i te f i r s , r e d c e d a r s , a nd S o u t he r np i n e s . T re es o f t h e se s p ec ie s a r e s m a l l e r i n d i a m et e r t h a n i s t h ec o a s t a l D o u g l a s f i r . A l a t h e was d e v e l o p e d t o a ccom mod ate l o g s w i t hd i a m e t e r s a s s m a l l a s 2 0 .3 t o 2 5 .4 cm ( 8 t o 1 0 i n . ) . 30

I n 1 96 4, t h e j e t v e ne er d r y e r r e p la c e d t h e r o l l e r d r y e r as m os te f f e c t i v e . The new j e t d r y e r s e n ab le d o u t p u t vo lu me t o d o ub l e , w h i l et h e nu mbe r o f e m pl oy ee s n e c e s s a r y r e m a in e d c o n s t a n t o r d e c r ea s e d .3 0

O t he r t e c h n o l o g i c a l changes t h a t i n c r e a se p r o d u c t i v i t y i n c l u d ea u t o m at ic c l i p p i n g o f v en ee r s h ee ts , p a ne l k n o t h o l e p a t c h i n g w i t h h o tp l a s t i c , a nd a u t o m a t i c h ig h -s p ee d h o t p r e s s l o a d i n g , c u r i n g , a n du n l o a d i n g . 21

REFERENCESI n d u s t r y a nd Tr ad e A d m i n i s t r a t i o n , U . S . De par tm ent o f Commerce.U . S . I n d u s t r i a l O u t l o o k 1 97 9. J a n u ar y 1 97 9. p . 4 0.1 98 0 D i r e c t o r y o f t h e F o r e s t P r od u ct s I n d u s t r y . San F r a n c i sc o ,M i l l e r Freeman P u b l i c a t i o n s , 1 98 0.L e t t e r f r o m Em ery , J . A . , A m e ri ca n Pl yw o o d A s s o c i a t i o n , t oM c C ar t hy , J. M . , R es ea rc h T r i a n g l e I n s t i t u t e . J a nu a ry 1 3 , 1 98 2.Comments on d r a f t C on t r o l Techn iques Document.Anderson , R. R e gi on a l P r o d u ct io n and D i s t r i b u t i o n P a t t e r n s o f t h eS o f t w ood P l yw ood I n du s t r y . A m er ic an P l y w ood A s s o c i a t i o n . E c onomi cR e p o r t E 31. Tacoma, Wa shin gton . June 1981.U .S . E n v i r onm en t a l P r o t e c t i o n A genc y. E conom ic A n a l y s i s o f P r oposedE f f l u e n t G u i d e l i n e s . The T im b er P r o c e s s i n s I n d u s t r y ( H ar d bo a rd .Wood Pre se rv i ng , P lywood and Veneer ) . E P A = ~ ~ O / -73-029 . A U ~ U S ~1973. p. 70.


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B e l l a s , C a r l . I n d u s t r i a l D emoc ra cy a nd t h e W o rke r Owned F i rm . NewY o r k , P r a e g e r P u b l i s h e r s . 1 97 2. p. 105.V a lu e L i n e I n v e s tme n t S u rve y s. A r n o l d B e r n h a r d & Company, NewYork , August 8 , 1980. p . 937, 940, 943, 953, 954, 956.Re fe re nce 8 , p . 931 .Ref ere nce 8 , p . 932, 934, 945, 951, 957.Bureau o f th e Census, U.S. Depar tmen t o f Commerce. 1977 Census o fM a n u f a c t u r e r s - - I n d u s t r y S e r i e s . MC 77-1-248. June 1980. p . 248-11.T e le c o n . E rb , K . , A m er ic an P l yw oo d A s s o c i a t i o n , w i t h C h e ss i n ,R o b e r t L . , R es ea rc h T r i a n g l e I n s t i t u t e . J u l y 29 , 1 98 1. R e co n s tr u c-t i o n o f e x i s t i n g ve neer d r y e r s .F r a n k l i n , E . C. P h en ot yp ic an d G e n e t ic V a r i a t i o n o f S u l f a t e N av elS t o r es Y i e l d s i n L o b l o l l y P in e. ( Pr es en te d a t TAPPI F o r e s t B i o l o g yC o n fe re n c e . San F ra n c i s c o . A p r i l 1 9 7 4. ) p . 9 9 .S p r i n g e r , E. L . L o ss es D u r i n g S to ra g e o f S o u th e rn P in e C h ip s .TAPPI. -9 :1 26 . A p r i l 1 97 6.H a jn g , G. J. O u ts id e S to ra g e o f P ulpw o od C h ip s . T AP PI. -9:97A.Oc tober 1966 .C o w l i n g , E . G . , e t a l . Changes i n V a lu e and U t i l i t y o f P ulpw oodD u r i n g H a r v e s t i n g , T r a n s p o r t , a nd S t o r a ge . TAPPI. -7:120.December 1974.L e t t e r f r o m M o r t e n s e n , D. K . , G e o r g i a - P a c i f ic C o r p o r a t i o n , t oMcCar thy , J. M . , R es ea rc h T r i a n g l e I n s t i t u t e , J a nu a ry 31 , 1 98 3.Comments on d r a f t Co n t ro l Techn iques Document.L e t t e r f r o m E m e r y , J. A . , A me r ic a n P ly w oo d A s s o c ia t i o n , t o Mc C a r th y,J. M . , R e s ea rch T r i a n g le I n s t i t u t e . D ece mb er 1 98 1. Comments o nd r a f t BID c h ap t e r s.V r a n i z a n , J. M. V en ee r D r y e r s - - T y p i c a l C o n s t r u c t i o n , O p e r a t i o n s ,and E f f l u e n t Abatem ent P o s s i b i l i t i e s . ( P r e se n t e d a t A i r P o l l u t i o nCo n t ro l As so c i a t io n . Eugene. November 17 , 1972 . )T e le c o n . C h e s s in , R . , R ese arch T r i a n g l e I n s t i t u t e , w i t h O e h l i n g,N . , Coe Ma n u fa c tu r i n g Company. O c to b e r 8 , 1 9 80 . I n fo rm a t i o n a b o u tv e n e e r d r y e r s .B rown ing , B. L . , ed. The Chem is t ry o f Wood. New York , I n te rs c i e n ceP u b l i s h e rs , 1 96 3. p . 3 18 .


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M on ro e, F. L ., e t a l . I n v e s t i g a t i o n o f E m i s si o n s f r o m P ly wo o dV en ee r D r y e r s , R e v is e d F i n a l R e p o r t. W a s hi ng t on S t a t e U n i v e r s i t y .P u l l m an , W as h i ng t on . F eb r ua r y 1972.C o r d e r , S. E. E n e rg y Use i n a n I n d u s t r i a l V e ne e r D r y e r . P ly wo o dResea rch Fo un da t io n. Tacoma, Wash ington. September 1975.C o r d e r , S . E. V e n t i l a t ' n g V en ee r D r y e r s. F o r e s t P r o d u c t s J o u r n a l .13: 449-453.- O c t obe r 1963 .E r b , C a r l . D r y e r s a n d V en ee r D r y i n g . A m e ri ca n P l yw o o d A s s o c i a t i o n .Tacoma, Wash ington. DFPA Te ch ni ca l Rep or t No. 112 , P a r t I. December1 9 7 5 . 1 3 p .L a i t y , W . W . , G. H. A t h e r t o n , a n d J. R. We1 ty . Compar isons o f A i rand S team as V enee r D r y i ng M ed ia . F o r e s t P r oduc t s J o u r na l . -4:21-29 .June 1974.Cronn, D. R . , e t a l . S t u d y o f t h e Pr op o se d a nd C h em ic al P r o p e r t i e so f A t m os p he r i c A e r o so l s A t t r i b u t a b l e t o P ly wo od V en ee r D r y e rE m i s s i o n s - - F i n a l R e p o r t t o A m e ri ca n P ly w o od A s s o c i a t i o n . W a s h i ng t o nS t a t e U n i v e r s i t y . P u l lm an , W a sh i ng t on . J un e 1 98 1.Te lecon . McCar thy , J. M. , Re search T r i a n g l e I n s t i t u t e , w i t hD a l l o n s , V . , NCASI. Mar ch 24, 1983 .L e t t e r f ro m B l o s se r , R. O . , N a t i o n a l C o u n c i l o f t h e Pa pe r I n d u s t r yf o r A i r and S t r eam I m p rov em en t, I n c . , t o F a r m er, J., U.S. Env i ronmenta lP r o t e c t i o n A ge ncy. J a n u a r y 1 9 , 19 83 . Comments o n d r a f t C o n t r o lTechniques Document .Lambuth. A . L . A d h e s iv e s i n t h e P l yw o o d I n d u s t r y . A d h e s iv e A ge.38 : 21-26 . A p r i 1 1977.-F a r r i s , M. R. The Veneer and P lywood In d u s t r y : Above AverageP r o d u c t i v i t y G a i n s, M o n t h l y L a b or R evie w. B u re a u o f La bo rS t a t i s t i c s , U.S. D e p a r t m e n t o f L a b or . S ep te mb er 1 97 8 . p . 28 .I n d u s t r y a n d T r a d e A d m i n i s t r a t i o n , U.S. D e p a r tm e n t o f Commerce,U. S. I n d u s t r i a l O u t l o o k 1 97 4. J a n u ar y 1 97 4. p . 5 4.


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3. EMISSION CONTROL TECHNIQUES

3 . 1 INTRODUCTIONC o n t r o l l i n g e m is s i on s f r o m p ly w oo d v en ee r d r y e r s b e g i ns w i t h

m a i n t a i n i n g d o or s e a l s , d r y e r s k i n s , t o p s , a nd b a f f l e s ; p r o p e r b a l a n c i n go f a i r f l o w s ; and use o f e nd - se a l i n g s e c t i o ns t o m in i mi z e f u g i t i v ee m i s s i o n s . S t a c k e m i s s i o n s f r o m p l y w o o d v e n e e r d r y e r s a n d p a n e l s a n de r sc a n b e s t b e c o n t r o l l e d b y a dd -o n e qu ip m en t. The s t r a t e g y f o r r e d u c i n gv e n e e r d r y e r e m i s s i o n s h a s c e n t e r e d on r em o v a l o f t h e o r g an i c a e ro s o lc om po ne nt t o re d u c e p lu m e o p a c i t y . Wet s c r u b b i n g an d i n c i n e r a t i o n a r et h e m os t common c o n t r o l t e c h ni q ue s f o r ve ne er d r y e r s . F a b r i c f i l t r a t i o nr e p re s e n ts c u r r e n t t e c hn o l og y f o r c o n t r o l o f s a n d er d us t e m is s i on s; b u ts u f f i c i e n t b lo w o u t p a n e l s , h a l o n d e l u ge s ys te ms , s p a r k d e t e c t o r s , a nda b o r t g a t e s m u s t b e ad de d t o m i t i g a t e t h e f i r e h a z a rd . l3 . 2 VENEER DRYER EMISSION CONTROL3 . 2 . 1 W e t S c r u b b i n gT he m os t common t e c h n o l o g y f o r v e n e er d r y e r s i s w e t s c r u b b i n g , f o rw h i c h s e v e r a l t y p e s o f e qu ip m en t a r e a v a i l a b l e . I n e ac h c as e, a w a t e rs p r ay i s i n t r o d u c e d i n t o t h e d r y e r e xh au st s tr ea m, r e s u l t i n g i n c o o l i n gan d c o nd e ns i ng o f o r g a n i c m a t e r i a l . Wa te r vapo r may condense on to theo r g a n i c a e r o s o l , 2 a nd t h e r e s u l t i n g d r o p l e t s a r e l a r g e e nough t o b eremoved b y c y c l o n i c c o l l e c t o r s , f i l t e r s , o r m i s t e l i m i n a t o r s . O rg an icm a t e r i a l t h a t r e m ai ns i n t h e v ap or p ha se es ca pe s c o l l e c t i o n an d re ac he st h e a tm os ph er e. T h e r e f o r e , w e t s c r u b b i n g w i l l h av e a l o w o r g a n i ce m i s si o n s r em o va l e f f i c i e n c y i f a p p l i e d t o v en ee r d r y e r e m i s si o ns w i t hh i g h ga se ou s f r a c t i o n s .

S c ru bb e rs e m p l oy i n g a number o f d i f f e r e n t c o l l e c t i o n m echanismsh av e b ee n u se d t o c o n t r o l v e n e er d r y e r e m is s i o ns . R e p r e s e n t a t i v e


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exa mples o f t h e s e c o l l e c t o r t y p es a r e d e s c r i b e d i n t h e f o l l o w i n g s ub sec-t i o n s . T he se s ys te m s h av e o n l y b ee n u s ed a t N o r t h w e s t e r n p l a n t s . Nos ys te ms h av e b ee n i n s t a l l e d a t p l a n t s d r y i n g S o u t h er n woods.

3 . 2 . 1 . 1 Mu1 t i p l e S p r a y C ha mbe rs. T he B u r l e y S c r u b b e r , t h e m o s tcommon w e t s c r u b b i n g d e v i c e u s ed to d a y , e mp lo ys t h r e e t o f i v e s p r a yc ha mb ers i n s e r i e s . The f i ve - c h am b e r m ode l c o n t a i n s a f i n a l dem i s t i n gz on e w he re a h i g h- s p e ed c e n t r i f u g a l f a n re mo ve s d r o p l e t s . The t h r e e -ch am be r m o de l, w h i c h i s c u r r e n t l y b e i n g m a r ke te d , r e q u i r e s n o f a n an dha s a n o p e r a t i n g p r e s s u r e dr o p o f o n l y 6 2 t o 1 2 4 Pa (0 .2 5 t o 0 .5 0 i n .w a t e r ) . The th re e -z o ne u n i t i s r e p o r t e d t o m ee t O r eg o n' s 1 0 p e r c e n to p a c i t y l i m i t on d r y e r e x ha us ts t h a t hav e m o i s t u r e c o n te n t s o f a t l e a s t24 p e r c e n t b y v 0 1 u m e . ~ T h i s d e v i c e i s d es ig ne d t o t r e a t t h e e xh au s tf ro m a s i n g l e s te am -h ea te d o r g a s - f i r e d d r y e r a nd g e n e r a l l y i s i n s t a l l e da bo ve t h e d r y e r . C h ap te r 6 c o n t a i n s t h e r 2 s u l t s o f e m i s s i on s t e s t s o fB u r l e y S cr u b b er s a nd s e v e r a l o t h e r w e t - s c r u b b i n g d e v i c e s . The re m o va le f f i c i e n c y o f B u r l e y S cru bb er s f o r p a r t i c u l a t e a nd c o n de n s i b l e e m is s i on sg e n e r a l l y i s l e s s t h a n 50 p e r c e n t . F rom r e c e n t O re go n D e p ar tm e n t o fE n v i ro n m e n ta l Q u a l i t y (ODEQ) M e th o d 7 t e s t s , ODEQ r e p o r t s t h a t t h i ss c r u b b e r c a n 1 i m i t p a r t i c u l a t e a nd c o n d e n s ib l e e m i ss i o ns t o 3 . 2 g/m2,9.5-mm b a s i s ( 0 .65 l b /1 , 000 f t 2 , 0 . 3 7 5 - i n . b a s i s ) , f o r W e s te r n w oo ds .3

3 . 2 . 1 . 2 C o m b i n a t i o n Pa c k ed T o we r a nd C y c l o n i c C o l 1e c t o r s . A ne x a m pl e o f a c o m b in a t io n p ac ke d t ow e r a nd c y c l o n i c c o l l e c t o r i s t h eG e o r g i a - P a c i f i c E m i s s i o n E l i m i n a t o r (now m a r k et e d b y Coe M a n u f a c t u r i n gCompany), w h i c h c o n s i s t s o f a s p ra y s e c t i o n f o l l o w e d b y a b a nk o f 2 t o1 2 c y c l o n e s i n p a r a 1 e l a nd a p a ck e d s p r a y t o w e r . The p a ck e d t o w e rmay b e e q ui p pe d w i t h f i b e r - p a d m i s t e l i m i n a t o r s . A s c h e m a ti c d i a g r a m o ft h e s ys te m i s g i v e n i n F i g u r e 3-1 . G e o r g i a - P a c i f i c E m i ss i on E l m i n a t o r shave be en i n s t a l l e d t o t r e a t t h e e xh au st s o f f ro m one t o t h r e e steam-h ea te d o r d i r e c t - f i r e d v en ee r d r y e r s . Because o f t h e i r s i z e , t h e u n i t sa r e i n s t a l l e d o u t s i d e o f t h e b u i l d i n g s ho us in g t h e d r y e r s . O v e r a l lp r e s s u r e d r o p a c r o s s s u c h a s ys t em i s a p p r o x i m a t e l y 2 ,8 60 Pa ( 11 .5 i n .w a t e r ) w i t h o u t t h e m i s t e l i m i n a t o r an d 4,85 0 Fa ( 19 . 5 i n . w a t e r ) w i t ht h e m i s t e l i m i n a t ~ r . ~E mi ss io n t e s t r e s u l t s f o r t he se u n i t s a r e g i v e ni n C ha pt er 6 . Removal e f f i c i e n c i e s f o r p a r t i c u l a t e an d c o n d en s i b l e


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o r g an i c em i s s i on s have been measu red t h r ou gh ODEQ M e t hod 7 a t up t o59 p e r c e n t w i t h o u t t h e m i s t e l i m i n a t o r a nd up t o 9 1 p e r c en t w i t h t h em i s t e l i m i n a t o r . ODEQ r e p o r t s t h a t t h e se u n i t s w i t h m i s t e l i m i n a t o r scan l i m i t p a r t i c u l a t e a nd co n d e n s i b l e e m i s s io n s t o 1 . 2 g /m2, 9.5-mmb a s i s ( 0 .2 5 1b/1,000 f t 2 , 0 .3 75 - i n . b a s i s ) , f o r s t e a m -h e a te d a n d g as -f i r e d d r y e r s ; 1 . 6 g/m 2, 9.5-mm b a s i s ( 0 .3 5 l b / 1 ,0 0 0 f t 2 , 0 . 3 7 5 - i n .b a s i s ) , f o r w o o d - f i r e d d r y e r s w i t h f u e l m o i s t u r e c o n t e n t l e s s t h a n20 pe rc e n t ; and 1 . 8 g /m2, 9.5-mm b a s i s (0 .40 lb /1 ,00 0 f t 2 , 0 . 3 7 5 - i n .b a s i s) , f o r w o o d - f i r ed d r y e r s w i t h f u e l m o i s t u r e c o n t e n t o f 20 p e r ce n to r g r e a te r .

V a r i o u s s i m p l e w e t- s c ru b b i n g d e v ic e s h a ve be en i n s t a l l e d onN o r t h w es t e rn v en ee r d r y e r s i n t h e p a s t 1 0 y e a r s . M os t o f t h e s e w e ts c r u b b e r s n e ve r h av e r e c e i v e d w i d e s p re a d u se . E m i s si o n r e d u c t i o n s o ft he se u n i t s a r e n o t e xp ec te d t o b e b e t t e r t h an t h os e o f t h e B u r l e y a n dG e or gi a- Pa ci f i c s c r ub b e r s w i t h o u t m i s t e l m i n a t o r s . E m i s s i o n s d a ta f o rt wo u n i t s , t h e B u c h h o lz S c ru b b e r an d t h e L e ck e nb y S c r u b b e r, a r e g i v e n i nC hap t e r 6.

3 . 2 . 1 . 3 S and F i l t e r S c ru b b e rs . The R ad er S a n d Ai r F i l t e r is ad e v i c e i n c o r p o r a t i n g a w e t - sc r u b b in g s e c t i o n f o l l o w e d b y a w e t- sa n df i l t e r and m i s t e l i m i n a t o r . F i g u r e 3 -2 i s a sch em at i c d ia gra m o f t h es yste m. The R ad er S a nd A ir F i l t e r h as be en i n s t a l l e d a t more t h a n s i xp ly w oo d p l a n t s i n t h e N o r t h w e ~ t . ~ x i s t i n g sys tems t r e a t t h e e xh au stf ro m tw o o r m ore st ea m- he at ed d r y e r s . The l a r g e r p a r t i c u l a t e m a t e r i a li s r em oved i n t h e s c r u bb e r , w h i l e a p o r t i o n o f t h e r e m a in i ng o rg a n i cm a t e r ia l i s c o l l e c t e d i n th e f i l t e r bed o r t h e m i s t e l i m i n a t o r . A w a t e rs pr ay c a r r i e s t h e co nd ense d m a t e r i a l t h r ou g h t h e f i l t e r b ed t o a s ep ara -t i o n s y s t e m . The d e s i g n p re s s u re d ro p o f t h e S a n dA ir u n i t i s a p p r o x i -m a t e l y 4 ,5 00 kP a ( 1 8 i n . w a t e r ) . E m is si on d a ta f o r t h i s d e v ic e a r es um m ar iz ed i n C h a p t e r 6 . The r e s u l t s i n d i c a t e t h a t up t o 90 p e r c e n t o fp a r t i c u l a t e a nd c o n d e n s i b l e o r g a n i c m a t e r i a l ( as d e f i n e d b y ODEQ M et ho d 7 )may be removed by th e S and Air sys tem.

3 . 2 . 1 . 4 I o n i z i n g Wet S c ru b b e rs . I o n i z i n g w e t s c ru b b e r s h av e b ee nu n d er de ve lo p me n t as v e n e er d r y e r e m i s s i o n c o n t r o l d e v i c e s f o r s e v e r a ly e a r s. S e v er a l C e i l c o t e I o n i z i n g Wet S cr ub b er s ha ve b ee n i n s t a l l e d o nd r y e r s i n t h e N o r t h ~ e s t . ~The C e i l c o t e u n i t has f o u r m ai n c o l l e c t i o n


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f e a t u r e s : (1) a w a t e r s p ra y ; ( 2 ) p ac ke d t o w e rs ; ( 3) e l e c t r o s t a t i cc o l l e c t i o n p l a t e s ; a nd ( 4) a m i s t e l i m i n a t o r . One p ac ke d t o w e r i sp l a ce d on each s i d e o f t h e c o l l e c t i o n p l a t e s . C e i l c o t e makes b o t hs i n g l e - a nd d u a l - s t a g e u n i t s , t h e d ua l -s t ag e u ni t . s h a v i n g tw o s e t s o fc o l l e c t i o n p l a t e s p l a c e d i n s e r ie s . A l t h o u g h no e m i s s i o n d a t a h av e be enp u b l i s h e d s ho win g re mo va l e f f i c i e n c i e s o f f u l l - s c a l e u n i t s , a p i l o t u n i td e m o n s tr a te d 5 7 t o 8 4 p e r c e n t r em o va l o f p a r t i c u l a t e an d c o n d en s ib l eorgan ic em iss ions as measured by ODEQ Method 7 .1 ODEQ has summarizeds e v e r a l t e s t s o f e x ha u st s f ro m f u l l - s c a l e u n i t s . The a g e n cy ' s c o n c l u s i o ni s t h a t C e i l c o t e u n i t s c an l i m i t p a r t i c u l a t e an d c o n d e n s i b le e m is s io n st o 1 . 2 g /m2, 9.5-mm b a s i s (0 .25 lb /1 ,0 00 ft2,0 . 3 75 - in . b a s i s ) , f o rs t eam - hea ted and g a s - f i r e d d r y e r s ; 1 . 6 g/m 2, 9.5-mm b as i s ( 0 . 35 1b /1,000 f t 2 , 0 .3 7 5- in . b a s i s ) , f o r w o o d - f i r e d d r y e r s w i t h f u e l m o i s t u r ec o n t e n t l e s s t h a n 20 p e r c e n t ; a nd 1 . 8 g/m 2, 9.5-mm b a s i s ( 0 . 4 0 1b /1,000 f t 2 , 0 .3 75 - i n. b a s i s ) , f o r w o o d - f i r e d d r y e r s w i t h f u e l m o i s t u r ec o n t e n t o f 20 p e r c e n t o r g r e a t e r . 3 I o n i z i n g w e t s c ru b b e rs h ave o n l yb ee n u se d o n w o o d - f i r e d a nd g a s - f i r e d d r y e r s .3 . 2. 2 I n c i n e r a t i o n

V en ee r d r y e r e m i s si o n s a r e c o n t r o l l e d a t some l o c a t i o n s b y i n c i n e r a -t i o n i n w o o d - f i r e d b o i l e r s o r f ur na ce s . The e n t i r e e xh a us t f l o w f ro m as te am -h e at ed v e ne e r d r y e r s om etim es c a n b e s e n t t o a b o i l e r , w h i l e o n l ya p o r t i o n o f t h e e xh au s t f ro m a d i r e c t - f i r e d d r y e r i s n o r m a l ly r e t u r n e dt o t h e f ur na ce o r f u e l c e l l . A t l e a s t one S o u th er n p l a n t ha s d i r e c t -f i r e d d r y e r s w i t h e xh a us t ga s r e c y c l e t o t h e f u r n a c e , b u t no s uc h s ys te msh ave b ee n t e s t e d f o r e m i ss i on s r e mo v al . B o i l e r i n c i n e r a t i o n o f v e ne erd r y e r e m i s s i o n s h a s n o t b ee n d e m o n s tr a t e d o n a S o u t h e r n p i n e v e n e e rd r y e r . However , Georg ia -Pac i f i c l 1 r e p o r t s p r ob le ms w i t h d u c t i n g any t y p eo f S o u th e rn p i n e d r y e r e x ha u st f o r an y d i s t a n c e b eca use o f c o n d en s at io n .C o nden sa t io n o f t e n o cc ur s i n t h e d r y e r , so i n s u l a t i o n i s o f l i t t l e v a lu e .I n s uc h c as es , s te am t r a c i n g o f t h e d u c t s may b e a v i a b l e a l t e r n a t i v e ,a l t h o u g h i t has n o t be en d em o ns tr at ed i n t h i s a p p l i c a t i o n .

3 . 2 . 2 .1 B o i l e r I n c i n e r a t i o n . B o i l e r i n c i n e r a t i o n sys te ms havebeen i n s t a l l e d i n a t l e a s t 13 p l a n t s i n t h e N or th we st . l2W i th t h i sm eth od, d r y e r e x ha u st i s u se d as c o mb us ti on a i r i n t h e b o i l e r . D r y e r


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e x ha u s t can be in t r o d u c e d as u n d e r f i r e a i r a nd /o r o v e r f i r e a i r . Them ost s o p h i s t i c a t e d s ys te ms i n v o l v e a ut o m at ic d i s t r i b u t i o n o f d r y e re x h a u s t as o v e r f i r e a n d u n d e r f i r e a i r , a c c o r d i n g t o ste am demand. l2

Because n o a d d i t i o n a l c om bu st io n d e vi c e i s r e q u i r e d i n b o i l e ri n c i n e r a t i o n , t h e ma in c a p i t a l e x p e n d i t u r es a r e f o r du c tw o rk , f a ns ,p r es su r e c o n t r o l l e r s , and b o i l e r o v e r s i z i n g o r m o d i f i c a t i o n s . A l l d u c t sa r e h e a v i l y i n s u l a t e d t o p r e v e n t c o n de n sa t i on o f d r y e r e m is s i on s .B o i l e r m o d i f i c a t i o n s i n c lu d e i n s t a l l i n g w a te r - co o le d g r a te s as w e l l asp o r t s f o r i n t r o d u c i n g d r y e r e xh au st . l2D r y e r e x h a u s t h as b e en d u c t e d t ob o i l e r s l o c a t e d o v e r 350 m f r o m t h e d r y e r . l3

S e v er a l g e n e r a l i z a t i o n s c a n b e made a b o u t b o i l e r i n c i n e r a t i o ns y st em s. F u r nac e t em p e r a t u r e s o f 1,190 ' C (2 ,000 ' F ) o r g r ea t e r a r ef ou n d i n m os t w o o d - f i r e d b o i l e r s . 1 4 R es id en ce t im e s f o r f u e l i n t h ef u r n ac e s e c t i o n a r e on t h e o r d e r o f 2.5 s f o r s p re a d er -s to k e r b o i l e r s ,b u t co m b u st io n a i r r e s i d e n c e t i m e may be l e s s f o r t h e s e a n d d u tc h -o v e nb o i l e r s . T he se t e m p e r a t u r e s a nd r e s i d e n c e t i m e s a r e a b ov e t h e m in im umr e q u ir e m e n t s f o r t h e rm a l d e s t r u c t i o n o f h y d ro ca rb o ns . l5T h e r e f o r e ,d e s t r u c t i o n e f f i c i e n c y may be l a r g e l y a f u n c t i o n o f t h e t u r b u l e nc e o rd eg re e o f m i x i n g i n t h e h i g h- te m pe ra tu re a re a o f t h e b o i l e r s . B o i l e rd e s i g ns p r o v i d e f o r a h i g h d e gr ee o f m i x i n g t o p ro m ot e co m bu st io n o fv o l a t i l e m a t e r i a l s f ro m t h e f u e l . T em p er at ur e a nd r e s i d e n c e t i m e c on -s i d e r a t i o n s s u p p or t t h e p o t e n t i a l f o r a h i g h , o v e r a l l re mova l r a t e o ft o t a l v en e er d r y e r e m is s io n s ( p er ha ps g r e a t e r t h a n 90 p e r c e n t ) b y b o i l e ri n c i n e r a t i o n . However, a t l e a s t t wo a t t e m p t s t o m ea su re t h e d e s t r u c t i o ne f f i c i e n c y o f t h e s e sy st em s f o r t o t a l o r g a n i c e m i s s i on s ha ve be en u ns uc-c e s s f u l . A re mo va l r a t e f o r c o n d en s ib l e o r g a n i c m a t e r i a l o f a p p r o x i m a te l y7 0 p e r c e n t was s u g g e st e d b y t h e r e s u l t s o f on e t e s t ( se e C h a p t e r 6 ) . Aw e t - sc r u b b in g d e v i c e o n t h e b o i l e r e x h au s t may be r e q u i r e d t o m ee t ah i g h l e v e l o f e mi ss io n s r e d u c t i o n .

B o i l e r i n c i n e r a t i o n may n o t be a v i a b l e c o n t r o l t e ch n iq u e f o rc e r t a i n e x i s t i n g p l a n t s . The co m bi ne d d r y e r e x h a u s t vo lu m e f o r a t y p i c a lp l y w o o d m i l l a pp ro ache s t h e c a p a c i t y o f t h e p l a n t b o i l e r t o a c c ep tc o m b u s t io n a i r . I n some c a se s , t h a t c a p a c i t y may b e e xc ee de d. F o rexample, newer b o i l e r s t h a t a r e de s i gn e d t o o p e r a te e f f i c i e n t l y on


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r e l a t i v e l y l o w ex ce ss a i r m i g h t be u n a b le t o a c c e p t t h e e x h a us t vo lum ef ro m a l l d r y e r s . F o r t h i s re a s on a l s o , new b o i l e r s m i g h t h av e t o beo v e rs i z e d t o a c co mmod ate t h e s y stem.

3 .2 .2 .2 I n c i n e r a t i o n i n a F ue l C e l l . The t e ch n o lo g y f o r h e a t i n gd r y e r s w i t h wood-waste f u e l has d e ve lo p ed c o n s id e r a b l y i n t h e l a s t 10y e a rs . The p r oc e ss in vo :v es b u r n i n g f u e l i n a f u r na c e o r

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